This application claims priority from Korean Patent Application No. 2002-69256, filed on Nov. 8, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to an apparatus and a method of driving a plasma display panel (PDP), and more particularly, to an apparatus and a method of driving a high-efficiency PDP for quickly eliminating a free-wheeling current, which is generated due to the parasitic effect in an energy recovery circuit, and improving the energy recovery efficiency.
2. Description of the Related Art
In general, a plasma display panel (PDP) is a flat display for displaying characters or images using plasma generated by gas discharge. Pixels ranging from several hundreds of thousands to more than millions, according to the size of the PDP, are arranged in the form of a matrix.
FIG. 1 shows a conventional alternating current (AC)-PDP sustain-discharge driver suggested by L. F. Weber, which includes an energy recovery unit with a clamping diode for suppressing the surge voltages of switches Sr, Ss, Sf, and Sd. The panel is assumed to have capacitor Cp as a load to analyze PDP driving circuit. FIG. 2 shows graphs of an output panel voltage Vp and a current IL flowing through an inductor L, according to a switching sequence. The AC-PDP sustain-discharge driver operates in the following four modes, according to the switching sequence.
1) Mode 1
A both-end panel voltage Vp is sustained at 0V when a switch Sx2 (not shown; a metal-oxide-semiconductor field effect transistor (MOSFET) corresponding to the switch Sd of a side 2 sustain-discharge driver) is turned on just before the switch Sr functioning as the MOSFET is turned on. Once the switch Sr is turned on, the AC-PDP sustain-discharge driver begins to operate in mode 1. In mode 1, an LC resonance circuit is formed through a path of the energy recovery capacitor Cc, the switch Sr, the diode Dr, the inductor L, and the capacitor Cp, as shown in FIG. 3A. Therefore, the current IL flows through the inductor L and the output voltage Vp of the panel increases. As a result, the current IL flowing through the inductor L becomes 0A, and the output voltage Vp of the panel becomes voltage +Vpk.
2) Mode 2
In mode 2, the switch Sr is turned off, and the switch Ss is turned on. The both-end voltage at switch Ss is changed from the voltage +Vpk to the voltage +Vs, which causes switching voltage loss. The voltage difference between the voltage +Vpk and the voltage +Vs is due to the parasitic components of the driver, such as parasitic capacitors or parasitic resistances. As shown in FIG. 3B, this voltage difference between the voltage +Vpk and the voltage +Vs causes a free-wheeling current that flows through a path of the switch Ss, the inductor L, and the diode D1. As shown in FIG. 2, the free-wheeling current decreases slowly because the both-end voltage at inductor L becomes about 2V, i.e., the voltage drop level of the diode D1 and the switch Ss. In mode 2, the output voltage Vp of the panel is sustained at the voltage +Vs, and the discharge of the panel is sustained.
3) Mode 3
In mode 3, the switch Sf is turned on and the switch Ss is turned off. The LC resonance circuit is formed through a path of the capacitor Cp, the inductor L, the diode Df, the switch Sf, and the energy recovery capacitor Cc. Therefore, the current IL flows through the inductor L, and the output voltage Vp of the panel decreases. As a result, the current IL flowing through the inductor L becomes 0 A and the output voltage Vp of the panel becomes equal to the voltage difference between the voltage +Vpk and the voltage +Vs.
4) Mode 4
In mode 4, the switch Sd is turned on and the switch Sf is turned off. The both-end voltage at switch Sd is changed from the voltage Vs−Vpk into 0V rapidly, which causes switching loss. The voltage difference between the voltage +Vpk and the voltage +Vs is due to the parasitic components of the driver, such as parasitic capacitors or parasitic resistances. As shown in FIG. 3D, this voltage difference between the voltage +Vpk and the voltage +Vs causes the free-wheeling current which flows through a path of the diode D2, the inductor L, and the switch Sd. As shown in FIG. 2, the free-wheeling current decreases slowly because both-end voltage at the inductor L becomes about 2V, i.e., the voltage drop level of the diode D2 and the switch Sd.
Thereafter, the switch Sx2 is turned off, and a switch Sx1 (not shown; a MOSFET corresponding to the switch Sr of a side 2 sustain-discharge driver) is turned on. Then, the process returns to the operation of mode 1, and the operations of mode 1 through 4 are repeated.
However, the free-wheeling current generated in the AC-PDP sustain-discharge driver causes the following problems.
First, since the free-wheeling current is very strong, i.e., about 30 A, it increases the stress which is applied to components through which the free-wheeling current flows, such as the switch Ss, the switch Sd, the inductor L, the diode D1, and the diode D2. As a result, high-current standard components must be used in the driver, which increases the size and production cost of the driver.
Second, the free-wheeling current increases the power consumption of the AC-PDP sustain-discharge driver.
Third, the free-wheeling current makes it difficult to control the timing sequence on the rising and falling edges of the output voltage Vp of the panel. In other words, the free-wheeling current hinders the timing sequence control of a gate signal.